1. Field of the Invention
The present invention relates to a hammer device for a keyboard instrument, which is applied to a keyboard instrument, such as an electronic piano, and is configured to impart touch weight by a hammer pivotally moved in a manner interlocked with key depression.
2. Description of the Related Art
As a hammer device for a keyboard instrument, such as an electronic piano, there have conventionally been known ones disclosed e.g. in Japanese Laid-Open Patent Publications (Kokai) No. 2011-22472 and No. 2004-341321, respectively. Each of the keyboard devices to which these hammer devices are applied, respectively, is comprised of a plurality of keys each extending in a front-rear direction, a plurality of hammers provided in association with the respective keys, and a keyboard chassis for pivotally supporting the keys and the hammers thereon in a state arranged side by side in a left-right direction.
The hammer disclosed in Japanese Laid-Open Patent Publication (Kokai) No. 2011-22472 is comprised of a hammer body formed as a resin molded article and a metal weight detachably attached to the hammer body. The hammer body is formed in a predetermined shape extending in the front-rear direction, and has a front half thereof pivotally supported on the keyboard chassis and a rear half thereof formed with a weight mounting portion having a predetermined shape. On the other hand, the weight is formed by a metal plate extending in the front-rear direction. The weight has a front half formed with a mounted portion having a shape complementary to the weight mounting portion of the hammer body, and extends from the mounted portion to a location close to the rear end of the keyboard chassis. The weight is configured such that it can be fixed to the hammer body by being slid forward in a state in which the mounted portion is fitted in the weight mounting portion of the hammer body, and can be removed from the hammer body by being slid rearward from the state fixed to the hammer body.
The keyboard chassis is formed as a molded article made of a synthetic resin, such as an ABS resin. The keyboard chassis has a large number of vertical ribs formed so as to ensure strength and rigidity of the keyboard chassis itself while maintaining a space for pivotal motion of each hammer which is performed in a manner interlocked with key depression. Specifically, each of the ribs is formed in a plate shape having a predetermined thickness in the left-right direction and is disposed in a manner separating hammers adjacent to each other in the left-right direction.
On the other hand, the hammer disclosed in Japanese Laid-Open Patent Publication (Kokai) No. 2004-341321 has a hammer body comprised of a resin holder and a metal base plate and two weight plates attached to left and right side surfaces of the hammer body, respectively. The hammer body is formed in a general S shape in side view by insert-molding the metal base plate in the resin holder. At predetermined locations on a front end of the metal base plate, there are formed a rivet hole and two positioning holes, respectively, each of which extends through the metal base plate in the left-right direction. On the other hand, the two weight plates are formed by respective metal plates having the same outer shape. Each of the weight plates has two positioning projections and rivet holes formed at respective predetermined locations on a hammer body-side surface. The two weight plates are fixed to the hammer body by sandwiching the metal base plate from both left and right sides and riveting rivets inserted through the rivet holes of the two weight plates and the metal base plate with each of the positioning projections fitted in an associated one of the positioning holes.
In an electronic piano having the hammer device disclosed in Japanese Laid-Open Patent Publication (Kokai) No. 2011-22472 or No. 2004-341321, the weight of each of hammers associated with respective keys in a lower-pitch range is made heavier than that of each of hammers associated with respective keys in a higher-pitch range so as to obtain touch weight of a keyboard closely analogous to touch weight of an acoustic piano during musical performance. For this reason, in general, in the hammer device, common hammer bodies are used for respective hammers, whereas a plurality of types of weights or weight plates different in shape from each other are used make the hammers different in weight according to each pitch range.
However, in the hammer device disclosed in Japanese Laid-Open Patent Publication (Kokai) No. 2011-22472, the shape of the mounted portion of the weight is common between the hammers, but it is required to form a plurality of protrusions at respective predetermined locations on the periphery of the mounted portion of the weight so as to facilitate removal of the weight from the hammer body, which makes the shape of the mounted portion complicated. Further, it is required to form a portion of the weight continuous with the mounted portion and extending rearward such that the shape of the portion largely differs on a pitch range basis. On the other hand, in the hammer device disclosed in Japanese Laid-Open Patent Publication (Kokai) No. 2004-341321, the two weight plates of each hammer are common in outer shape, but it is required to form the two positioning projections such that they project in different directions. In addition, the two weight plates of each hammer are required to be formed such that their shape largely differs on a pitch range basis.
As described above, the weight or the weight plate (hereinafter generically referred to as “the weight) employed in the hammer device disclosed in Japanese Laid-Open Patent Publication (Kokai) No. 2011-22472 or No. 2004-341321 has a complicated shape, and multiple types of weights are needed for a whole keyboard instrument. For this reason, multiple types of metal molds which enable a metal plate to be cut into complicated shapes are required so as to manufacture the above-mentioned weights, which results in increases manufacturing costs. In addition, since the shape of the weight is complicated, there is a fear that manufacturing efficiency and yield are lower.
Further, assuming that the electronic piano is stored in a room in an upright position in which the left and right sides thereof are in vertically opposite positions, if the room temperature becomes very high e.g. in summer, the keyboard chassis made of a synthetic resin and the hammer body tend to be bent downward due to the self weight of the keyboard chassis and the weight of the hammers, which can cause deformation of the keyboard chassis and the hammer body. In this case, there is a possibility that noise is generated during musical performance e.g. due to rubbing of the metal weight of a hammer in pivotal motion against an associated one of the synthetic resin-made vertical ribs of the keyboard chassis. To avoid this, during manufacturing of the electronic piano, a guide tape having lubricity is wound around a portion of the weight of each hammer, which can rub against a vertical rib associated therewith, for example, whereby noise generated due to rubbing of the weight of the hammer against the keyboard chassis is largely reduced.
However, in general, the keyboard device of an electronic piano is provided with the same number (e.g. eighty-eight) of hammers as the number of keys. For this reason, when it is required to wind the guide tape around the weight of each of all the hammers, the tape winding work takes much time and labor and necessitates the guide tape, which causes an increase in manufacturing cost.